The charge transfer devices may be analog shift registers as are, for example, arrayed in parallel in charge-coupled device (CCD) imagers to store and to transport charge packets descriptive of the picture elements (pixels) in an image. The image is typically in the visible or infrared electromagnetic spectrum. In order to achieve optimal transfer efficiencies, particularly where the number of electrons per pixel sample is low, bias charges must be introduced into the stages of the analog shift registers as they are vacated of previous charge packets during each charge transfer cycle. Introduction of these bias charges is done using a further analog shift register which is receptive of bias charges at its input and which supplies the bias charges from respective ones of its stages to the inputs of the analog shift registers in parallel array.
A problem is encountered with the bias charge introduced during one charge transfer cycle being apt to differ slightly from that introduced during another charge transfer cycle. This generates a type of noise accompanying the signal described on an analog sampling basis by the charge packets in the analog shift register.